Storing money in a decimal column - what precision and scale

Question

I m using a decimal column to store money values on a database  and today I was wondering what precision and scale to use   Since supposedly char columns of a fixed width are more efficient  I was thinking the same could be true for decimal columns  Is it   And what precision and scale should I use  I was thinking precision 24 8  Is that overkill  not enough or ok     This is what I ve decided to do    Store the conversion rates  when applicable  in the transaction table itself  as a float Store the currency in the account table The transaction amount will be a DECIMAL 19 4  All calculations using a conversion rate will be handled by my application so I keep control of rounding issues   I don t think a float for the conversion rate is an issue  since it s mostly for reference  and I ll be casting it to a decimal anyway   Thank you all for your valuable input

User · Answer

I would think that for a large part your or your client s requirements should dictate what precision and scale to use  For example  for the e-commerce website I am working on that deals with money in GBP only  I have been required to keep it to Decimal  6  2

User · Answer

Sometimes you will need to go to less than a cent and there are international currencies that use very large demoniations   For example  you might charge your customers 0 088 cents per transaction   In my Oracle database the columns are defined as NUMBER 20 4

User · Answer

If you re going to be doing any sort of arithmetic operations in the DB  multiplying out billing rates and so on   you ll probably want a lot more precision than people here are suggesting  for the same reasons that you d never want to use anything less than a double-precision floating point value in application code

User · Answer

If you are looking for a one-size-fits-all  I d suggest DECIMAL 19  4  is a popular choice  a quick Google bears this out   I think this originates from the old VBA Access Jet Currency data type  being the first fixed point decimal type in the language  Decimal only came in  version 1 0  style  i e  not fully implemented  in VB6 VBA6 Jet 4 0   The rule of thumb for storage of fixed point decimal values is to store at least one more decimal place than you actually require to allow for rounding  One of the reasons for mapping the old Currency type in the front end to DECIMAL 19  4  type in the back end was that Currency exhibited bankers  rounding by nature  whereas DECIMAL p  s  rounded by truncation   An extra decimal place in storage for DECIMAL allows a custom rounding algorithm to be implemented rather than taking the vendor s default  and bankers  rounding is alarming  to say the least  for a designer expecting all values ending in  5 to round away from zero    Yes  DECIMAL 24  8  sounds like overkill to me  Most currencies are quoted to four or five decimal places  I know of situations where a decimal scale of 8  or more  is required but this is where a  normal  monetary amount  say four decimal places  has been pro rata d  implying the decimal precision should be reduced accordingly  also consider a floating point type in such circumstances   And no one has that much money nowadays to require a decimal precision of 24     However  rather than a one-size-fits-all approach  some research may be in order  Ask your designer or domain expert about accounting rules which may be applicable  GAAP  EU  etc  I vaguely recall some EU intra-state transfers with explicit rules for rounding to five decimal places  therefore using DECIMAL p  6  for storage  Accountants generally seem to favour four decimal places     PS Avoid SQL Server s MONEY data type because it has serious issues with accuracy when rounding  among other considerations such as portability etc  See Aaron Bertrand s blog     Microsoft and language designers chose banker s rounding because hardware designers chose it  citation    It is enshrined in the Institute of Electrical and Electronics Engineers  IEEE  standards  for example  And hardware designers chose it because mathematicians prefer it  See Wikipedia  to paraphrase  The 1906 edition of Probability and Theory of Errors called this  the computer s rule    computers  meaning humans who perform computations

User · Answer

The money datatype on SQL Server has four digits after the decimal   From SQL Server 2000 Books Online   Monetary data represents positive or negative amounts of money  In Microsoft   SQL Server    2000  monetary data is stored using the money and smallmoney data types  Monetary data can be stored to an accuracy of four decimal places  Use the money data type to store values in the range from -922 337 203 685 477 5808 through  922 337 203 685 477 5807  requires 8 bytes to store a value   Use the smallmoney data type to store values in the range from -214 748 3648 through 214 748 3647  requires 4 bytes to store a value   If a greater number of decimal places are required  use the decimal data type instead

User · Answer

When handling money in MySQL  use DECIMAL 13 2  if you know the precision of your money values or use DOUBLE if you just want a quick good-enough approximate value  So if your application needs to handle money values up to a trillion dollars  or euros or pounds   then this should work   DECIMAL 13  2    Or  if you need to comply with GAAP then use   DECIMAL 13  4

User · Answer

If you were using IBM Informix Dynamic Server  you would have a MONEY type which is a minor variant on the DECIMAL or NUMERIC type   It is always a fixed-point type  whereas DECIMAL can be a floating point type    You can specify a scale from 1 to 32  and a precision from 0 to 32  defaulting to a scale of 16 and a precision of 2    So  depending on what you need to store  you might use DECIMAL 16 2  - still big enough to hold the US Federal Deficit  to the nearest cent - or you might use a smaller range  or more decimal places

User · Answer

The money datatype on SQL Server has four digits after the decimal   From SQL Server 2000 Books Online   Monetary data represents positive or negative amounts of money  In Microsoft   SQL Server    2000  monetary data is stored using the money and smallmoney data types  Monetary data can be stored to an accuracy of four decimal places  Use the money data type to store values in the range from -922 337 203 685 477 5808 through  922 337 203 685 477 5807  requires 8 bytes to store a value   Use the smallmoney data type to store values in the range from -214 748 3648 through 214 748 3647  requires 4 bytes to store a value   If a greater number of decimal places are required  use the decimal data type instead

User · Answer

If you re going to be doing any sort of arithmetic operations in the DB  multiplying out billing rates and so on   you ll probably want a lot more precision than people here are suggesting  for the same reasons that you d never want to use anything less than a double-precision floating point value in application code

User · Answer

4 decimal places would give you the accuracy to store the world s smallest currency sub-units  You can take it down further if you need micropayment  nanopayment    accuracy   I too prefer DECIMAL to DBMS-specific money types  you re safer keeping that kind of logic in the application IMO  Another approach along the same lines is simply to use a  long  integer  with formatting into   unit subunit for human readability       currency symbol  done at the application level

User · Answer

If you are looking for a one-size-fits-all  I d suggest DECIMAL 19  4  is a popular choice  a quick Google bears this out   I think this originates from the old VBA Access Jet Currency data type  being the first fixed point decimal type in the language  Decimal only came in  version 1 0  style  i e  not fully implemented  in VB6 VBA6 Jet 4 0   The rule of thumb for storage of fixed point decimal values is to store at least one more decimal place than you actually require to allow for rounding  One of the reasons for mapping the old Currency type in the front end to DECIMAL 19  4  type in the back end was that Currency exhibited bankers  rounding by nature  whereas DECIMAL p  s  rounded by truncation   An extra decimal place in storage for DECIMAL allows a custom rounding algorithm to be implemented rather than taking the vendor s default  and bankers  rounding is alarming  to say the least  for a designer expecting all values ending in  5 to round away from zero    Yes  DECIMAL 24  8  sounds like overkill to me  Most currencies are quoted to four or five decimal places  I know of situations where a decimal scale of 8  or more  is required but this is where a  normal  monetary amount  say four decimal places  has been pro rata d  implying the decimal precision should be reduced accordingly  also consider a floating point type in such circumstances   And no one has that much money nowadays to require a decimal precision of 24     However  rather than a one-size-fits-all approach  some research may be in order  Ask your designer or domain expert about accounting rules which may be applicable  GAAP  EU  etc  I vaguely recall some EU intra-state transfers with explicit rules for rounding to five decimal places  therefore using DECIMAL p  6  for storage  Accountants generally seem to favour four decimal places     PS Avoid SQL Server s MONEY data type because it has serious issues with accuracy when rounding  among other considerations such as portability etc  See Aaron Bertrand s blog     Microsoft and language designers chose banker s rounding because hardware designers chose it  citation    It is enshrined in the Institute of Electrical and Electronics Engineers  IEEE  standards  for example  And hardware designers chose it because mathematicians prefer it  See Wikipedia  to paraphrase  The 1906 edition of Probability and Theory of Errors called this  the computer s rule    computers  meaning humans who perform computations

User · Answer

If you are looking for a one-size-fits-all  I d suggest DECIMAL 19  4  is a popular choice  a quick Google bears this out   I think this originates from the old VBA Access Jet Currency data type  being the first fixed point decimal type in the language  Decimal only came in  version 1 0  style  i e  not fully implemented  in VB6 VBA6 Jet 4 0   The rule of thumb for storage of fixed point decimal values is to store at least one more decimal place than you actually require to allow for rounding  One of the reasons for mapping the old Currency type in the front end to DECIMAL 19  4  type in the back end was that Currency exhibited bankers  rounding by nature  whereas DECIMAL p  s  rounded by truncation   An extra decimal place in storage for DECIMAL allows a custom rounding algorithm to be implemented rather than taking the vendor s default  and bankers  rounding is alarming  to say the least  for a designer expecting all values ending in  5 to round away from zero    Yes  DECIMAL 24  8  sounds like overkill to me  Most currencies are quoted to four or five decimal places  I know of situations where a decimal scale of 8  or more  is required but this is where a  normal  monetary amount  say four decimal places  has been pro rata d  implying the decimal precision should be reduced accordingly  also consider a floating point type in such circumstances   And no one has that much money nowadays to require a decimal precision of 24     However  rather than a one-size-fits-all approach  some research may be in order  Ask your designer or domain expert about accounting rules which may be applicable  GAAP  EU  etc  I vaguely recall some EU intra-state transfers with explicit rules for rounding to five decimal places  therefore using DECIMAL p  6  for storage  Accountants generally seem to favour four decimal places     PS Avoid SQL Server s MONEY data type because it has serious issues with accuracy when rounding  among other considerations such as portability etc  See Aaron Bertrand s blog     Microsoft and language designers chose banker s rounding because hardware designers chose it  citation    It is enshrined in the Institute of Electrical and Electronics Engineers  IEEE  standards  for example  And hardware designers chose it because mathematicians prefer it  See Wikipedia  to paraphrase  The 1906 edition of Probability and Theory of Errors called this  the computer s rule    computers  meaning humans who perform computations

User · Answer

When handling money in MySQL  use DECIMAL 13 2  if you know the precision of your money values or use DOUBLE if you just want a quick good-enough approximate value  So if your application needs to handle money values up to a trillion dollars  or euros or pounds   then this should work   DECIMAL 13  2    Or  if you need to comply with GAAP then use   DECIMAL 13  4

User · Answer

Sometimes you will need to go to less than a cent and there are international currencies that use very large demoniations   For example  you might charge your customers 0 088 cents per transaction   In my Oracle database the columns are defined as NUMBER 20 4

User · Answer

If you were using IBM Informix Dynamic Server  you would have a MONEY type which is a minor variant on the DECIMAL or NUMERIC type   It is always a fixed-point type  whereas DECIMAL can be a floating point type    You can specify a scale from 1 to 32  and a precision from 0 to 32  defaulting to a scale of 16 and a precision of 2    So  depending on what you need to store  you might use DECIMAL 16 2  - still big enough to hold the US Federal Deficit  to the nearest cent - or you might use a smaller range  or more decimal places

User · Answer

4 decimal places would give you the accuracy to store the world s smallest currency sub-units  You can take it down further if you need micropayment  nanopayment    accuracy   I too prefer DECIMAL to DBMS-specific money types  you re safer keeping that kind of logic in the application IMO  Another approach along the same lines is simply to use a  long  integer  with formatting into   unit subunit for human readability       currency symbol  done at the application level

User · Answer

4 decimal places would give you the accuracy to store the world s smallest currency sub-units  You can take it down further if you need micropayment  nanopayment    accuracy   I too prefer DECIMAL to DBMS-specific money types  you re safer keeping that kind of logic in the application IMO  Another approach along the same lines is simply to use a  long  integer  with formatting into   unit subunit for human readability       currency symbol  done at the application level

User · Answer

If you were using IBM Informix Dynamic Server  you would have a MONEY type which is a minor variant on the DECIMAL or NUMERIC type   It is always a fixed-point type  whereas DECIMAL can be a floating point type    You can specify a scale from 1 to 32  and a precision from 0 to 32  defaulting to a scale of 16 and a precision of 2    So  depending on what you need to store  you might use DECIMAL 16 2  - still big enough to hold the US Federal Deficit  to the nearest cent - or you might use a smaller range  or more decimal places

User · Answer

We recently implemented a system that needs to handle values in multiple currencies and convert between them  and figured out a few things the hard way   NEVER USE FLOATING POINT NUMBERS FOR MONEY  Floating point arithmetic introduces inaccuracies that may not be noticed until they ve screwed something up  All values should be stored as either integers or fixed-decimal types  and if you choose to use a fixed-decimal type then make sure you understand exactly what that type does under the hood  ie  does it internally use an integer or floating point type    When you do need to do calculations or conversions    Convert values to floating point Calculate new value Round the number and convert it back to an integer   When converting a floating point number back to an integer in step 3  don t just cast it - use a math function to round it first  This will usually be round  though in special cases it could be floor or ceil  Know the difference and choose carefully   Store the type of a number alongside the value  This may not be as important for you if you re only handling one currency  but it was important for us in handling multiple currencies  We used the 3-character code for a currency  such as USD  GBP  JPY  EUR  etc   Depending on the situation  it may also be helpful to store    Whether the number is before or after tax  and what the tax rate was  Whether the number is the result of a conversion  and what it was converted from    Know the accuracy bounds of the numbers you re dealing with  For real values  you want to be as precise as the smallest unit of the currency  This means you have no values smaller than a cent  a penny  a yen  a fen  etc  Don t store values with higher accuracy than that for no reason   Internally  you may choose to deal with smaller values  in which case that s a different type of currency value  Make sure your code knows which is which and doesn t get them mixed up  Avoid using floating point values even here     Adding all those rules together  we decided on the following rules  In running code  currencies are stored using an integer for the smallest unit   class Currency      String code            eg  USD     int value              eg 2500    boolean converted     class Price      Currency grossValue     Currency netValue     Tax taxRate      In the database  the values are stored as a string in the following format   USD 2500   That stores the value of  25 00  We were able to do that only because the code that deals with currencies doesn t need to be within the database layer itself  so all values can be converted into memory first  Other situations will no doubt lend themselves to other solutions     And in case I didn t make it clear earlier  don t use float

User · Answer

If you re going to be doing any sort of arithmetic operations in the DB  multiplying out billing rates and so on   you ll probably want a lot more precision than people here are suggesting  for the same reasons that you d never want to use anything less than a double-precision floating point value in application code

User · Answer

I would think that for a large part your or your client s requirements should dictate what precision and scale to use  For example  for the e-commerce website I am working on that deals with money in GBP only  I have been required to keep it to Decimal  6  2

User · Answer

The money datatype on SQL Server has four digits after the decimal   From SQL Server 2000 Books Online   Monetary data represents positive or negative amounts of money  In Microsoft   SQL Server    2000  monetary data is stored using the money and smallmoney data types  Monetary data can be stored to an accuracy of four decimal places  Use the money data type to store values in the range from -922 337 203 685 477 5808 through  922 337 203 685 477 5807  requires 8 bytes to store a value   Use the smallmoney data type to store values in the range from -214 748 3648 through 214 748 3647  requires 4 bytes to store a value   If a greater number of decimal places are required  use the decimal data type instead

User · Answer

We recently implemented a system that needs to handle values in multiple currencies and convert between them  and figured out a few things the hard way   NEVER USE FLOATING POINT NUMBERS FOR MONEY  Floating point arithmetic introduces inaccuracies that may not be noticed until they ve screwed something up  All values should be stored as either integers or fixed-decimal types  and if you choose to use a fixed-decimal type then make sure you understand exactly what that type does under the hood  ie  does it internally use an integer or floating point type    When you do need to do calculations or conversions    Convert values to floating point Calculate new value Round the number and convert it back to an integer   When converting a floating point number back to an integer in step 3  don t just cast it - use a math function to round it first  This will usually be round  though in special cases it could be floor or ceil  Know the difference and choose carefully   Store the type of a number alongside the value  This may not be as important for you if you re only handling one currency  but it was important for us in handling multiple currencies  We used the 3-character code for a currency  such as USD  GBP  JPY  EUR  etc   Depending on the situation  it may also be helpful to store    Whether the number is before or after tax  and what the tax rate was  Whether the number is the result of a conversion  and what it was converted from    Know the accuracy bounds of the numbers you re dealing with  For real values  you want to be as precise as the smallest unit of the currency  This means you have no values smaller than a cent  a penny  a yen  a fen  etc  Don t store values with higher accuracy than that for no reason   Internally  you may choose to deal with smaller values  in which case that s a different type of currency value  Make sure your code knows which is which and doesn t get them mixed up  Avoid using floating point values even here     Adding all those rules together  we decided on the following rules  In running code  currencies are stored using an integer for the smallest unit   class Currency      String code            eg  USD     int value              eg 2500    boolean converted     class Price      Currency grossValue     Currency netValue     Tax taxRate      In the database  the values are stored as a string in the following format   USD 2500   That stores the value of  25 00  We were able to do that only because the code that deals with currencies doesn t need to be within the database layer itself  so all values can be converted into memory first  Other situations will no doubt lend themselves to other solutions     And in case I didn t make it clear earlier  don t use float

User · Answer

The money datatype on SQL Server has four digits after the decimal   From SQL Server 2000 Books Online   Monetary data represents positive or negative amounts of money  In Microsoft   SQL Server    2000  monetary data is stored using the money and smallmoney data types  Monetary data can be stored to an accuracy of four decimal places  Use the money data type to store values in the range from -922 337 203 685 477 5808 through  922 337 203 685 477 5807  requires 8 bytes to store a value   Use the smallmoney data type to store values in the range from -214 748 3648 through 214 748 3647  requires 4 bytes to store a value   If a greater number of decimal places are required  use the decimal data type instead

User · Answer

I would think that for a large part your or your client s requirements should dictate what precision and scale to use  For example  for the e-commerce website I am working on that deals with money in GBP only  I have been required to keep it to Decimal  6  2

User · Answer

Sometimes you will need to go to less than a cent and there are international currencies that use very large demoniations   For example  you might charge your customers 0 088 cents per transaction   In my Oracle database the columns are defined as NUMBER 20 4

User · Answer

A late answer here  but I ve used  DECIMAL 13 2    which I m right in thinking should allow upto 99 999 999 999 99

User · Answer

If you re going to be doing any sort of arithmetic operations in the DB  multiplying out billing rates and so on   you ll probably want a lot more precision than people here are suggesting  for the same reasons that you d never want to use anything less than a double-precision floating point value in application code

User · Answer

I would think that for a large part your or your client s requirements should dictate what precision and scale to use  For example  for the e-commerce website I am working on that deals with money in GBP only  I have been required to keep it to Decimal  6  2

User · Answer

If you were using IBM Informix Dynamic Server  you would have a MONEY type which is a minor variant on the DECIMAL or NUMERIC type   It is always a fixed-point type  whereas DECIMAL can be a floating point type    You can specify a scale from 1 to 32  and a precision from 0 to 32  defaulting to a scale of 16 and a precision of 2    So  depending on what you need to store  you might use DECIMAL 16 2  - still big enough to hold the US Federal Deficit  to the nearest cent - or you might use a smaller range  or more decimal places

User · Answer

If you are looking for a one-size-fits-all  I d suggest DECIMAL 19  4  is a popular choice  a quick Google bears this out   I think this originates from the old VBA Access Jet Currency data type  being the first fixed point decimal type in the language  Decimal only came in  version 1 0  style  i e  not fully implemented  in VB6 VBA6 Jet 4 0   The rule of thumb for storage of fixed point decimal values is to store at least one more decimal place than you actually require to allow for rounding  One of the reasons for mapping the old Currency type in the front end to DECIMAL 19  4  type in the back end was that Currency exhibited bankers  rounding by nature  whereas DECIMAL p  s  rounded by truncation   An extra decimal place in storage for DECIMAL allows a custom rounding algorithm to be implemented rather than taking the vendor s default  and bankers  rounding is alarming  to say the least  for a designer expecting all values ending in  5 to round away from zero    Yes  DECIMAL 24  8  sounds like overkill to me  Most currencies are quoted to four or five decimal places  I know of situations where a decimal scale of 8  or more  is required but this is where a  normal  monetary amount  say four decimal places  has been pro rata d  implying the decimal precision should be reduced accordingly  also consider a floating point type in such circumstances   And no one has that much money nowadays to require a decimal precision of 24     However  rather than a one-size-fits-all approach  some research may be in order  Ask your designer or domain expert about accounting rules which may be applicable  GAAP  EU  etc  I vaguely recall some EU intra-state transfers with explicit rules for rounding to five decimal places  therefore using DECIMAL p  6  for storage  Accountants generally seem to favour four decimal places     PS Avoid SQL Server s MONEY data type because it has serious issues with accuracy when rounding  among other considerations such as portability etc  See Aaron Bertrand s blog     Microsoft and language designers chose banker s rounding because hardware designers chose it  citation    It is enshrined in the Institute of Electrical and Electronics Engineers  IEEE  standards  for example  And hardware designers chose it because mathematicians prefer it  See Wikipedia  to paraphrase  The 1906 edition of Probability and Theory of Errors called this  the computer s rule    computers  meaning humans who perform computations

User · Answer

4 decimal places would give you the accuracy to store the world s smallest currency sub-units  You can take it down further if you need micropayment  nanopayment    accuracy   I too prefer DECIMAL to DBMS-specific money types  you re safer keeping that kind of logic in the application IMO  Another approach along the same lines is simply to use a  long  integer  with formatting into   unit subunit for human readability       currency symbol  done at the application level

User · Answer

A late answer here  but I ve used  DECIMAL 13 2    which I m right in thinking should allow upto 99 999 999 999 99

User · Answer

We recently implemented a system that needs to handle values in multiple currencies and convert between them  and figured out a few things the hard way   NEVER USE FLOATING POINT NUMBERS FOR MONEY  Floating point arithmetic introduces inaccuracies that may not be noticed until they ve screwed something up  All values should be stored as either integers or fixed-decimal types  and if you choose to use a fixed-decimal type then make sure you understand exactly what that type does under the hood  ie  does it internally use an integer or floating point type    When you do need to do calculations or conversions    Convert values to floating point Calculate new value Round the number and convert it back to an integer   When converting a floating point number back to an integer in step 3  don t just cast it - use a math function to round it first  This will usually be round  though in special cases it could be floor or ceil  Know the difference and choose carefully   Store the type of a number alongside the value  This may not be as important for you if you re only handling one currency  but it was important for us in handling multiple currencies  We used the 3-character code for a currency  such as USD  GBP  JPY  EUR  etc   Depending on the situation  it may also be helpful to store    Whether the number is before or after tax  and what the tax rate was  Whether the number is the result of a conversion  and what it was converted from    Know the accuracy bounds of the numbers you re dealing with  For real values  you want to be as precise as the smallest unit of the currency  This means you have no values smaller than a cent  a penny  a yen  a fen  etc  Don t store values with higher accuracy than that for no reason   Internally  you may choose to deal with smaller values  in which case that s a different type of currency value  Make sure your code knows which is which and doesn t get them mixed up  Avoid using floating point values even here     Adding all those rules together  we decided on the following rules  In running code  currencies are stored using an integer for the smallest unit   class Currency      String code            eg  USD     int value              eg 2500    boolean converted     class Price      Currency grossValue     Currency netValue     Tax taxRate      In the database  the values are stored as a string in the following format   USD 2500   That stores the value of  25 00  We were able to do that only because the code that deals with currencies doesn t need to be within the database layer itself  so all values can be converted into memory first  Other situations will no doubt lend themselves to other solutions     And in case I didn t make it clear earlier  don t use float

User · Answer

Sometimes you will need to go to less than a cent and there are international currencies that use very large demoniations   For example  you might charge your customers 0 088 cents per transaction   In my Oracle database the columns are defined as NUMBER 20 4

User · Answer

We recently implemented a system that needs to handle values in multiple currencies and convert between them  and figured out a few things the hard way   NEVER USE FLOATING POINT NUMBERS FOR MONEY  Floating point arithmetic introduces inaccuracies that may not be noticed until they ve screwed something up  All values should be stored as either integers or fixed-decimal types  and if you choose to use a fixed-decimal type then make sure you understand exactly what that type does under the hood  ie  does it internally use an integer or floating point type    When you do need to do calculations or conversions    Convert values to floating point Calculate new value Round the number and convert it back to an integer   When converting a floating point number back to an integer in step 3  don t just cast it - use a math function to round it first  This will usually be round  though in special cases it could be floor or ceil  Know the difference and choose carefully   Store the type of a number alongside the value  This may not be as important for you if you re only handling one currency  but it was important for us in handling multiple currencies  We used the 3-character code for a currency  such as USD  GBP  JPY  EUR  etc   Depending on the situation  it may also be helpful to store    Whether the number is before or after tax  and what the tax rate was  Whether the number is the result of a conversion  and what it was converted from    Know the accuracy bounds of the numbers you re dealing with  For real values  you want to be as precise as the smallest unit of the currency  This means you have no values smaller than a cent  a penny  a yen  a fen  etc  Don t store values with higher accuracy than that for no reason   Internally  you may choose to deal with smaller values  in which case that s a different type of currency value  Make sure your code knows which is which and doesn t get them mixed up  Avoid using floating point values even here     Adding all those rules together  we decided on the following rules  In running code  currencies are stored using an integer for the smallest unit   class Currency      String code            eg  USD     int value              eg 2500    boolean converted     class Price      Currency grossValue     Currency netValue     Tax taxRate      In the database  the values are stored as a string in the following format   USD 2500   That stores the value of  25 00  We were able to do that only because the code that deals with currencies doesn t need to be within the database layer itself  so all values can be converted into memory first  Other situations will no doubt lend themselves to other solutions     And in case I didn t make it clear earlier  don t use float

[sql] Storing money in a decimal column - what precision and scale?

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